Ideal Vaccine Candidate Research Articles

Evaluation in mice of cell-free produced CT584 as a Chlamydia vaccine antigen.

Chlamydia trachomatis is the most prevalent bacterial sexually transmitted pathogen worldwide. Since chlamydial infection is largely asymptomatic with the potential for serious complications, a preventative vaccine is likely the most viable long-term answer to this public health threat. Cell-free protein synthesis (CFPS) utilizes the cellular protein manufacturing machinery decoupled from the requirement for maintaining cellular viability, offering the potential for flexible, rapid, and de-centralized production of recombinant protein vaccine antigens. Here, we use CFPS to produce the putative chlamydial type three secretion system (T3SS) needle-tip protein, CT584, for use as a vaccine antigen in mouse models. High-speed atomic force microscopy (HS-AFM) imaging and computer simulations confirm that CFPS-produced CT584 retains a native-like structure prior to immunization. Female mice were primed with CT584 adjuvanted with CpG-1826 intranasally (i.n.) or CpG-1826 + Montanide ISA 720 intramuscularly (i.m.), followed four-weeks later by an i.m. boost before respiratory challenge with 104 inclusion forming units (IFU) of Chlamydia muridarum. Immunization with CT584 generated robust antibody responses but weak cell mediated immunity and failed to protect against i.n. challenge as demonstrated by body weight loss, increased lungs' weights and the presence of high numbers of IFUs in the lungs. While CT584 alone may not be the ideal vaccine candidate, the speed and flexibility with which CFPS can be used to produce other potential chlamydial antigens makes it an attractive technique for antigen production.

An engineered Accum-E7 protein-based vaccine with dual anti-cervical cancer activity.

Worldwide prevalence of cervical cancer decreased significantly with the use of human papilloma virus (HPV)-targeted prophylactic vaccines. However, these multivalent antiviral vaccines are inert against established tumors, which leave patients with surgical ablative options possibly resulting in long-term reproductive complications and morbidity. In an attempt to bypass this unmet medical need, we designed a new E7 protein-based vaccine formulation using Accum™, a technology platform designed to promote endosome-to-cytosol escape as a means to enhance protein accumulation in target cells. Prophylactic vaccination of immunocompetent mice using the Accum-E7 vaccine (aE7) leads to complete protection from cervical cancer despite multiple challenges conducted with ascending C3.43 cellular doses (0.5-, 1.0-, and 2.0 × 106 cells). Moreover, the humoral response induced by aE7 was higher in magnitude compared with naked E7 protein vaccination and displayed potent inhibitory effects on C3.43 proliferation invitro. When administered therapeutically to animals with pre-established C3.43 or Tal3 tumors, the vaccine-induced response synergized with multiple immune checkpoint blockers (anti-PD-1, anti-CTLA4, and anti-CD47) to effectively control tumor growth. Mechanistically, the observed therapeutic effect requires cross-presenting dendritic cells as well as CD8 T cells predominantly, with a non-negligible role played by both CD4+ and CD19+ lymphocytes. good laboratory practice (GLP) studies revealed that aE7 is immunogenic and well tolerated by immunocompetent mice with no observed adverse effects despite the use of a fourfold exceeding dose. In a nutshell, aE7 represents an ideal vaccine candidate for further clinical development as it uses a single engineered protein capable of exhibiting both prophylactic and therapeutic activity.

In silico designing and characterization of outer membrane protein K (OmpK) from Vibrio anguillarum and its expression in Nicotiana tabacum for the development of a plant-based vaccine against fish vibriosis

Vibriosis is caused by Vibrio anguillarum in various species of aquaculture. A novel, secure, and stable vaccine is needed to eradicate vibriosis. Here, for reverse vaccinology and plant-based expression, the outer membrane protein K (OmpK) of V. anguillarum was chosen due to its conserved nature in all Vibrio species. OmpK, an ideal vaccine candidate against vibriosis, demonstrated immunogenic, non-allergic, and non-toxic behavior by using various bioinformatics tools. Docking showed the interaction of the OmpK model with TLR-5. In comparison to costly platforms, plants can be used as alternative and economic bio-factories to produce vaccine antigens. We expressed OmpK antigen in Nicotiana tabacum using Agrobacterium-mediated transformation. The expression vector was constructed using Gateway® cloning. Transgene integration was verified by polymerase chain reaction (PCR), and the copy number via qRT-PCR, which showed two copies of transgenes. Western blotting detected monomeric form of OmpK protein. The total soluble protein (TSP) fraction of OmpK was equivalent to 0.38% as detected by ELISA. Mice and fish were immunized with plant-derived OmpK antigen, which showed a significantly high level of anti-OmpK antibodies. The present study is the first report of OmpK antigen expression in higher plants for the potential use as vaccine in aquaculture against vibriosis, which could provide protection against multiple Vibrio species due to the conserved nature OmpK antigen.

SARS-CoV-2 spike protein S1 subunit induces potent neutralizing responses in mice and is effective against Delta and Omicron variants.

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, belongs to the betacoronavirus genus. This virus has a high mutation rate, which rapidly evolves into new variants with different properties, such as increased transmissibility or immune evasion. Currently, the most prevalent global SARS-CoV-2 variant is Omicron, which is more transmissible than previous variants. Current available vaccines may be less effective against some currently existing SARS-CoV-2 variants, including the Omicron variant. The S1 subunit of the spike protein of SARS-CoV-2 has been a major target for COVID-19 vaccine development. It plays a crucial role in the virus's entry into host cells and is the primary target for neutralizing antibodies. In this study, the S1 subunit of the spike protein of SARS-CoV-2 was engineered and produced at a high level in Nicotiana benthamiana plant. The expression level of the recombinant S1 protein was greater than the 0.5-g/kg fresh weight, and the purification yield was at least ~0.3 g of pure protein/kg of plant biomass, which would make a plant-produced S1 antigen an ideal vaccine candidate for commercialization. Purified, the plant-produced SARS-CoV-2 S1 protein exhibited significantly higher binding to the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2). Moreover, we also show that recombinant S1 protein/antigen-elicited antibodies can neutralize the Delta or Omicron variants. Collectively, our results demonstrate that a plant-produced S1 antigen could be a promising vaccine candidate against SARS-CoV-2 variants including Omicron.

Boosting Mouse Defense against Lethal Toxoplasma gondii Infection with Full-Length and Soluble SAG1 Recombinant Protein.

Toxoplasmosis is a major worldwide protozoan zoonosis. The surface antigen 1 (SAG1) of Toxoplasma gondii (T. gondii) has always been recognized as an ideal vaccine candidate antigen. However, the intact and soluble SAG1 protein is usually difficult to acquire in vitro, which is unfavorable for employing the recombinant protein as a vaccine candidate antigen. In the present study, we obtained the full-length SAG1 recombinant protein in soluble form by Escherichia coli Transetta (DE3) cells under optimized expression conditions. The immunogenicity and protective ability of this recombinant protein against T. gondii acute infection were evaluated in a mouse model. Monitoring changes in serum antibody levels and types, the presence of cytokines, and the rate of lymphocyte proliferation in vaccinated mice were used to assess humoral and cellular immune responses. Additional assessments were performed to determine the protective potency of the recombinant protein in combating T. gondii RH tachyzoites. It was found that the titers of both IgG2a and IgG2b were considerably greater in the immunized mice compared to the titers of IgG1 and IgG3. The levels of Th1-type cytokines (IFN-γ, IL-12p70, IL-2, and TNF-α) and Th2-type cytokines (IL-10) significantly increased when splenocytes from immunological group mice were treated with T. gondii lysate antigen. Compared to the control group, a recombinant protein substantially increased the longevity of infected mice, with an average death time prolonged by 14.50 ± 0.34 days (p < 0.0001). These findings suggest that the full-length and soluble SAG1 recombinant protein produced potent immune responses in mice and could be a preferred subunit vaccine candidate for T. gondii, offering a feasible option for vaccination against acute toxoplasmosis.

A story of Shigella vaccine development in ICMR-NICED involving multidimensional approaches

Enteric bacterial infection causes diarrhea throughout the world, especially in developing countries. Shigella is solely answerable toalmost 1.1 million deaths annually in the pediatric population. Vaccine development against diarrheal diseases is always an encouragedconcern. Our laboratory, dedicated to find a possible therapy against shigellosis, is working on a path of various potential methodologiesand immunogens. Over the years, we have concentrated and reported different immunogens with their advantages and drawbacks,ultimately leading us to find the best possible vaccine candidate against bloody diarrhea.The venture started with live attenuated vaccines that protect against multiple serotypes and subtypes of pathogens and found limitedhost-serotype specific immune responses. It was observed that introducing a lipopolysaccharide biosynthesis gene pPR 1347 in Shigelladysenteriae type 1, transformed it into an avirulent organism for candidate vaccine.A mutant strain of Shigella flexneri 2a lacking the RNA-binding protein Hfq was made, leading to increased expression of the type IIIsecretion system via loss of regulation, resulting in attenuation of cell viability through repression of stress response sigma factors. Suchincreased antigen production and simultaneous attenuation were expected to elicit protective immunity against homologous and alimited number of heterologous serotypes subtypes.Although we formulated the live attenuated vaccine through the introduction of a lipopolysaccharide gene and a mutant lackingRNA binding protein Hfq, but due to lack of heterologous protective efficacy, these were not an ideal vaccine candidate to be madeavailable in the market although they showed a significant amount of immunogenicity. Moreover, live attenuated strains always havea possibility to revert back to its virulent form.Subsequently, monovalent and hexavalent heat-killed immunogens with single and six Shigella serotypes have shown significantprotective efficacy in mice, and rabbit models. Recently we have shown the homologous as well some extent of heterologus protectiveefficacy of heat killed multi-serotype Shigella (HKMS) immunogens in a guinea pig colitis model.A novel formulation for improved immunogen delivery system comprises substantially effective amounts of alginate chitosannanoparticles with OmpA protein of Shigella species. Alginate chitosan nano formulations of OmpA consists essentially of OmpAprotein as conserved active molecule, but efficacy study reveals partial protection efficacy against present circulating Shigella. Furtherimproving the delivery system, we have also formulated a subunit-based vaccine by nanoformulation of ipaC protein of Shigella. Themain drawback of OmpA and ipaC subunit based vaccines are they cannot provide a broad spectrum protection against 50 subtypesand serotypes of Shigella, although they act as a conserved protein in Enterobacteriaceae family, indicating single epitope cannot bethe sole factor associated with the operational protective efficacy.Eventually, our research moved a step ahead and found next-generation outer membrane vesicles (OMVs) based antigens from Shigella.Disruption of tolA, one of the genes of the Tol–Pal system of Shigella membrane, has increased the OMVs release rate by approximately80% higher. Recently we have reported only four serotype-subtype cross-protection among 50 subtypes of circulating Shigella in micemodels. Outer membrane vesicles based immunogen could be a potential cost-effective non-living, next-generation candidate vaccineagainst shigellosis for humans.

Oral Immunization with Escherichia coli Nissle 1917 Expressing SARS-CoV-2 Spike Protein Induces Mucosal and Systemic Antibody Responses in Mice

As of October 2022, the COVID-19 pandemic continues to pose a major public health conundrum, with increased rates of symptomatic infections in vaccinated individuals. An ideal vaccine candidate for the prevention of outbreaks should be rapidly scalable, easy to administer, and able to elicit a potent mucosal immunity. Towards this aim, we proposed an engineered Escherichia coli (E. coli) Nissle 1917 (EcN) strain with SARS-CoV-2 spike protein (SP)-coding plasmid, which was able to expose SP on its cellular surface by a hybridization with the adhesin involved in diffuse adherence 1 (AIDA1). In this study, we presented the effectiveness of a 16-week intragastrically administered, engineered EcN in producing specific systemic and mucosal immunoglobulins against SARS-CoV-2 SP in mice. We observed a time-dependent increase in anti-SARS-CoV-2 SP IgG antibodies in the sera at week 4, with a titre that more than doubled by week 12 and a stable circulating titre by week 16 (+309% and +325% vs. control; both p < 0.001). A parallel rise in mucosal IgA antibody titre in stools, measured via intestinal and bronchoalveolar lavage fluids of the treated mice, reached a plateau by week 12 and until the end of the immunization protocol (+300, +47, and +150%, at week 16; all p < 0.001 vs. controls). If confirmed in animal models of infection, our data indicated that the engineered EcN may be a potential candidate as an oral vaccine against COVID-19. It is safe, inexpensive, and, most importantly, able to stimulate the production of both systemic and mucosal anti-SARS-CoV-2 spike-protein antibodies.

Vaccination with recombinant Toxoplasma gondii bradyzoite-formation deficient 1 (rTgBFD1) antigen provides partial protective immunity against chronic T. gondii infection.

As an apicomplexan pathogen, Toxoplasma gondii still remains a major threat to public health and requires special attention. In fact, positive attempts to identify more effective antigens to provide protection are important to control toxoplasmosis. Latest scientific advances in T. gondii study hint at the probability of the T. gondii bradyzoite-formation deficient 1 (TgBFD1) as an ideal vaccine candidate, since this molecule plays a critical role in regulating the chronic infection of T. gondii. Thus, BALB/c mouse models of acute and chronic T. gondii infections were used to evaluate the TgBFD1 protection efficacy in this study. Before conducting animal trials, antigen analysis of TgBFD1 was performed using DNAstar software and Western blots. The preliminary results suggested that TgBFD1 should be a potent immunogen. Then, this conclusion is confirmed by ELISA assays. After immunization with rTgBFD1, high levels of specific IgG, IgG1, IgG2a, and cytokines (Interferon γ and interleukin 10) were observed, indicating that TgBFD1 could induce strong protective antibody responses. While TgBFD1-specific IgG antibodies were measurable in vaccinated mice, no protection was observed in the acute T. gondii infection (RH strain) assay. However, a noticeable decrease in brain cysts counts of immunized mice compared with negative controls in the latent T. gondii infection (PRU strain) assay was observed. Taken together, these results indicated that rTgBFD1 had the remarkable ability to elicit both humoral and cellular immune responses and could provide partial protective immunity against chronic T. gondii infection.

The Development of a Multiplex Real-Time Quantitative PCR Assay for the Differential Detection of the Wild-Type Strain and the MGF505-2R, EP402R and I177L Gene-Deleted Strain of the African Swine Fever Virus.

Simple SummaryAfrican swine fever (ASF) was first reported in August 2018 in China, and the naturally gene-deleted ASFV strain was first identified in 2020 in this country. The vaccine candidates that deleted some virulent genes from the virulent parental strains have also been reported in many countries. To differentiate the wild-type and gene-deleted ASFV strains, four pairs of specific primers and TaqMan probes targeting the ASFV B646L (p72), I177L, MGF505-2R and EP402R (CD2v) genes were designed. After optimizing the reaction conditions, a multiplex real-time qPCR assay for the differential detection of the wild-type and gene-deleted ASFV strains was developed. The assay was further used to test 4239 clinical samples, and 534 samples were positive for ASFV, of which 30 samples lacked B646L, I177L, MGF505-2R and/or EP402R genes. The assay showed high specificity, sensitivity and repeatability, and it provided a reliable method for evaluating ASFV in clinical samples.African swine fever virus (ASFV) causes African swine fever (ASF), a devastating hemorrhagic disease of domestic pigs and wild boars. Currently, the MGF505R, EP402R (CD2v) and I177L gene-deleted ASFV strains were confirmed to be the ideal vaccine candidate strains. To develop an assay for differentiating the wild-type and gene-deleted ASFV strains, four pairs of specific primers and TaqMan probes targeting the ASFV B646L (p72), I177L, MGF505-2R and EP402R (CD2v) genes were designed. A multiplex real-time qPCR assay for the differential detection of the wild-type and gene-deleted ASFV strains was developed after optimizing the reaction conditions, including the annealing temperature, primer concentration and probe concentration. The results showed that the multiplex real-time qPCR assay can specifically test the ASFV B646L (p72), I177L, MGF505-2R and EP402R (CD2v) genes with a limit of detection (LOD) of 32.1 copies/μL for the B646L (p72) gene, and 3.21 copies/μL for the I177L, MGF505-2R and EP402R (CD2v) genes. However, the assay cannot test for the classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), porcine circovirus type 2 (PCV2), PCV3 and pseudorabies virus (PRV). The assay demonstrated good repeatability and reproducibility with coefficients of variation (CV) less than 1.56% for both the intra- and inter-assay. The assay was used to test 4239 clinical samples, and the results showed that 12.60% (534/4239) samples were positive for ASFV, of which 10 samples lacked the EP402R gene, 6 samples lacked the MGF505-2R gene and 14 samples lacked the EP402R and MGF505-2R genes. The results indicated that the multiplex real-time qPCR developed in this study can provide a rapid, sensitive and specific diagnostic tool for the differential detection of the ASFV B646L, I177L, MGF505-2R and EP402R genes.

Detection of Autotransporter Genes and Evaluation of the Relationship Between the Autotransporters and Biofilm Formation in Uropathogenic Escherichia Coli Isolated From Urinary Tract Infections

Background: Uropathogenic Escherichia coli (UPEC) are among the pathogens causing urinary tract infections (UTIs). UPEC strains utilize autotransporter (AT) proteins for pathogenesis, especially the development of biofilm in the urinary tract. Objective: There is no general data about the frequency of ATs among the UPECs, thus we decided to assess the frequency and AT patterns in patients with UPEC recovered from UTI, as well as to find the possible correlation between the ATs and biofilm. Materials and Methods: Totally, 200 Escherichia coli were recovered from the urine of outpatients and inpatients with UTIs in Iran. Biofilm production was assessed by a phenotypic method. Extraction of DNA was done using the boiling method, and the extracted products were used for polymerase chain reaction (PCR). Amplification of AT genes was done by PCR with an optimized program in a thermal cycler apparatus. Then, the amplified genes were evaluated by electrophoresis. Results: Among the UPEC isolates, 63.5% and 36.5% were isolated from cystitis and pyelonephritis patients, respectively. In addition, the majority of UPECs (66.5%) were associated with hospitalized patients. Totally, 92% of isolates produced biofilm, of which 53.5%, 21.5%, and 17% were weak, moderate, and strong biofilm producers, respectively. Among investigated ATs, the most frequent genes were upaH (89%), upaB (87%), upaG (79%), vat (78%), sat (69%), upaC (67%), and ag43 (37%). There were 37 AT patterns among UPECs, and pattern 1 with the presence of all AT genes was the most common. It was found that the prevalence of upaB and upaG was significantly higher among the cystitis isolates compared to pyelonephritis isolates. Further, no significant difference was observed between the AT genes, except for upaC (P=0.003), and the intensity of biofilm formation in UPEC isolates. Conclusion: According to the high prevalence of AT genes among UPECs isolated from inpatients and outpatients, these factors can be ideal vaccine candidates for designing effective vaccines against the isolates. Evaluation of the efficacy of these ATs against UPECs is under investigation.

A Single Vaccination of IBDV Subviral Particles Generated by Kluyveromyces marxianus Efficiently Protects Chickens against Novel Variant and Classical IBDV Strains

Infectious bursal disease (IBD), caused by the infectious bursal disease virus (IBDV), is a highly contagious and immunosuppressive disease in chickens worldwide. The novel variant IBDV (nvIBDV) has been emerging in Chinese chicken farms since 2017, but there are no available vaccines that can provide effective protection. Herein, the capsid protein VP2 from nvIBDV strain FJ-18 was expressed in Kluyveromyces marxianus with the aim to produce nvIBDV subviral particles (SVPs). Two recombinant strains constructed for expression of nvIBDV VP2 (nvVP2) and His-tagged VP2 (nvHVP2) formed two types of nvIBDV subviral particles (SVPs), namely nvVP2-SVPs and nvHVP2-SVPs. TEM scans showed that both SVPs were about 25 nm in diameter, but there was a large portion of nvVP2-SVPs showing non-spherical particles. Molecular dynamics simulations indicate that an N-terminal His tag strengthened the interaction of the nvHVP2 monomer and contributed to the assembly of SVPs. Vaccination of chicks with the nvHVP2-SVPs provided 100% protection against novel variant IBDV infection when challenged with the FJ-18 strain, as well as the classical strain BC6/85. By contrast, vaccination with the nvVP2-SVPs only provided 60% protection against their parent FJ-18 strain, suggesting that the stable conformation of subviral particles posed a great impact on their protective efficacy. Our results showed that the nvHVP2-SVPs produced by the recombinant K. marxianus strain is an ideal vaccine candidate for IBDV eradication.

COVID-eVax, an electroporated DNA vaccine candidate encoding the SARS-CoV-2 RBD, elicits protective responses in animal models

The COVID-19 pandemic caused by SARS-CoV-2 has made the development of safe and effective vaccines a critical priority. To date, four vaccines have been approved by European and American authorities for preventing COVID-19, but the development of additional vaccine platforms with improved supply and logistics profiles remains a pressing need. Here we report the preclinical evaluation of a novel COVID-19 vaccine candidate based on the electroporation of engineered, synthetic cDNA encoding a viral antigen in the skeletal muscle. We constructed a set of prototype DNA vaccines expressing various forms of the SARS-CoV-2 spike (S) protein and assessed their immunogenicity in animal models. Among them, COVID-eVax—a DNA plasmid encoding a secreted monomeric form of SARS-CoV-2 S protein receptor-binding domain (RBD)—induced the most potent anti-SARS-CoV-2 neutralizing antibody responses (including against the current most common variants of concern) and a robust T cell response. Upon challenge with SARS-CoV-2, immunized K18-hACE2 transgenic mice showed reduced weight loss, improved pulmonary function, and lower viral replication in the lungs and brain. COVID-eVax conferred significant protection to ferrets upon SARS-CoV-2 challenge. In summary, this study identifies COVID-eVax as an ideal COVID-19 vaccine candidate suitable for clinical development. Accordingly, a combined phase I-II trial has recently started.

Vaccinomics-driven proteome-wide screening of Haemophilus influenzae for the prediction of common putative vaccine candidates.

Haemophilus influenzae colonizes the respiratory tract and is associated with life-threatening invasive infections. The recent rise in its global prevalence, even in the presence of multiple vaccines, indicates an urgent need to develop effective cross-strain vaccine strategies. Our work focused on identifying the universally conserved antigenic regions of H. influenzae that can be used to develop new vaccines. A variety of bioinformatics tools were applied for the comprehensive geno-proteomic analysis of H. influenzae type a strain, as reference serotype, through which subcellular localization, essentiality, virulence, and non-host homology were determined. B and T cell epitope mapping of the 3D protein structures were performed. Thereafter, molecular docking with HLA_DRB1*0101 and comparative genome analysis established the candidature of the identified regions. Based on the established vaccinomics criteria, five target proteins were predicted as novel vaccine candidates. Among these, nine epitopic regions that could regulate lymphocyte activity through strong protein-protein interactions were identified. Comparative genomic analysis revealed that the identified regions were highly conserved among the different strains of H. influenzae. Based on multiple immunogenic factors, five prioritized proteins and their predicted epitopes were identified as ideal common putative vaccine candidates against typeable strains.

Hesitancy towards COVID-19 Vaccination among Healthcare Workers: A Multi-Centric Survey in France

Vaccination programs against COVID-19 are being scaled up. We aimed to assess the effects of vaccine characteristics on vaccine hesitancy among healthcare workers in a multi-center survey conducted within French healthcare facilities from 1 December 2020 to 26 March 2021. We invited any healthcare workers naïve of COVID-19 vaccination to complete an online self-questionnaire. They reported on their socio-demographic characteristics, as well as their perception and beliefs towards vaccination. We measured their willingness to get vaccinated in eight scenarios for candidates’ vaccines presented sequentially (1 to 4-point scale). Candidates’ vaccines varied for efficacy (25%, 50%, 100%), length of immunization (1 year or lifetime), frequency (<1/100, <1/10,000), and severity (none, moderate, severe) of adverse events. We analyzed 4349 healthcare workers’ responses with interpretable questionnaires. The crude willingness to get vaccinated was 53.2% and increased over time. We clustered the trajectories of responses using an unsupervised classification algorithm (k-means) and identified four groups of healthcare workers: those willing to get vaccinated in any scenario (18%), those not willing to get vaccinated at all (22%), and those hesitating but more likely to accept (32%) or reject (28%) the vaccination depending on the scenario. In these last two subgroups, vaccine acceptance was growing with age, educational background and was higher among men with condition. Compared to an ideal vaccine candidate, a 50% reduced efficacy resulted in an average drop in acceptance by 0.8 (SD ± 0.8, −23.5%), while it was ranging from 1.4 (SD ± 1.0, −38.4%) to 2.1 (SD ± 1.0, −58.4%) in case of severe but rare adverse event. The acceptance of a mandatory immunization program was 29.6% overall and was positively correlated to the willingness to get vaccinated, ranging from 2.4% to 60.0%. Even if healthcare workers represent a heterogeneous population, most (80%) could accept the vaccination against COVID-19. Their willingness to get the vaccine increased over time and as immunization programs became available. Among hesitant professionals, the fear of adverse events was the main concern. Targeted information campaigns reassuring about adverse events may increase vaccine coverage, in a population with a strong opinion about mandatory immunization programs.

Recombinant resuscitation-promoting factor protein of Nocardia seriolae, a promissing vaccine candidate for largemouth bass (Micropterus salmoides)

Nocardia seriolae is an important pathogenic bacterium that causes nocardiosis in various fish species and leads to economic losses in the fish industry. To develop an effective subunit vaccine against nocardial infection, the truncated resuscitation-promoting factor (tRPF) of N. seriolae was selected and recombinantly produced using the Escherichia coli expression system. Western blotting results indicated that the recombinant protein could be strongly recognised by largemouth bass anti-N. seriolae antibodies. The protective efficacy of tRPF recombinant protein was assessed in combination with the commercial adjuvant Montanide™ ISA 763 A VG. The results showed that emulsified tRPF + ISA significantly induced high serum antibody response and serum lysozyme activity in the vaccinated fish. Quantitative reverse transcription polymerase chain reaction analysis indicated that tRPF + ISA could notably enhance the expression of immune-related genes in both the head kidney and spleen of the vaccinated fish. Finally, vaccinated largemouth bass displayed higher immuno-protection with a relative percent survival of 69.23% compared to the control groups. Taken together, the combination of tRPF + ISA is an ideal vaccine candidate against N. seriolae infection.

Dangers of mRNA vaccines.

“Necessity is the mother of invention:” An adage was brought to life with the emergence of the mRNA vaccine against the backdrop of the foreboding and mercurial COVID-19 pandemic. Considering a negligible adverse-effect profile and a break-neck manufacturing speed, it shone bright as the ideal vaccine candidate. However, “all that glitters is not gold,” as was evidenced by the significant reactogenicity, a host of multi-systemic side-effects, that are being reported by the vaccine recipients; which is palpably resulting in a shift of emotions for the vaccine, accounting for vaccine hesitancy. Anaphylaxis, antibody-dependent enhancements, and deaths, comprise the most serious side-effects, albeit occurring in sparing numbers. Storage and transportation require fastidious temperatures, rendering it substantially inaccessible to a country like India. The biggest jolt, however, was the unfolding of the biases in reporting vaccine efficacy, as only the attractively high numbers of the relatively equivocal relative risk reduction were reported while keeping at bay the meager numbers of the more forthright absolute risk reduction. Notwithstanding the fallacies, the mRNA vaccine still promises hope; and with the right precautions and finesse, can be potentiated, as “a watched pot never boils.”

A Chimeric Plasmodium vivax Merozoite Surface Protein Antibody Recognizes and Blocks Erythrocytic P. cynomolgi Berok Merozoites In Vitro.

Research on erythrocytic Plasmodium vivax merozoite antigens is critical for identifying potential vaccine candidates in reducing P. vivax disease. However, many P. vivax studies are constrained by its inability to undergo long-term culture in vitro Conserved across all Plasmodium spp., merozoite surface proteins are essential for invasion into erythrocytes and highly expressed on erythrocytic merozoites, thus making it an ideal vaccine candidate. In clinical trials, the P. vivax merozoite surface protein 1 (PvMSP1-19) vaccine candidate alone has shown to have limited immunogenicity in patients; hence, we incorporate the highly conserved and immunogenic C terminus of both P. vivax merozoite surface protein 8 (PvMSP8) and PvMSP1-19 to develop a multicomponent chimeric protein rPvMSP8+1 for immunization of mice. The resulted chimeric rPvMSP8+1 antibody was shown to recognize native protein MSP8 and MSP1-19 of mature P. vivax schizonts. In the immunized mice, an elevated antibody response was observed in the rPvMSP8+1-immunized group compared to that immunized with single-antigen components. In addition, we examined the growth inhibition of these antibodies against Plasmodium cynomolgi (Berok strain) parasites, which is phylogenetically close to P. vivax and sustains long-term culture in vitro Similarly, the chimeric anti-rPvMSP8+1 antibodies recognize P. cynomolgi MSP8 and MSP1-19 on mature schizonts and showed strong inhibition in vitro via growth inhibition assay. This study provides support for a new multiantigen-based paradigm rPvMSP8+1 to explore potential chimeric vaccine candidates against P. vivax malaria using sister species P. cynomolgi.

COVID-19 coronavirus vaccine T cell epitope prediction analysis based on distributions of HLA class I loci (HLA-A, -B, -C) across global populations

ABSTRACT T cell immunity, such as CD4 and/or CD8 T cell responses, plays a vital role in controlling the virus infection and pathological damage. Several studies have reported SARS-CoV-2 proteins could serve as ideal vaccine candidates against SARS-CoV-2 infection by activating the T cell responses. In the current study, based on the SARS-CoV-2 sequence and distribution of host human leukocyte antigen (HLA), we predicted the possible epitopes for the vaccine against SARS-CoV-2 infections. Firstly, the current study retrieved the SARS-CoV-2 S and N protein sequences from the NCBI Database. Then, using the Immune Epitope Database Analysis Resource, we predicted the CTL epitopes of the SARS-CoV-2 S and N proteins according to worldwide frequency distributions of HLA-A, -B, and -C alleles (>1%). Our results predicted 90 and 106 epitopes of N and S proteins, respectively. Epitope cluster analysis showed 16 and 34 respective clusters of SARS-CoV-2 N and S proteins, which covered 95.91% and 96.14% of the global population, respectively. After epitope conservancy analysis, 8 N protein epitopes and 6 S protein epitopes showed conservancy within two SARS-CoV-2 types. Of these 14 epitopes, 13 could cover SARS coronavirus and Bat SARS-like coronavirus. The remaining epitope (KWPWYIWLGF1211-1220) could cover MERS coronavirus. Finally, the 14-epitope combination could vaccinate 89.60% of all individuals worldwide. Our results propose single or combined CTL epitopes predicted in the current study as candidates for vaccines to effectively control SARS-CoV-2 infection and development.

Analysis of Putative Epitope Candidates of Mycobacterium tuberculosis Against Pakistani Human Leukocyte Antigen Background: An Immunoinformatic Study for the Development of Future Vaccine.

Tuberculosis (TB), a chronic disease caused by Mycobacterium tuberculosis (Mtb), is a global health issue across the world. Pakistan ranks fifth among the countries, which are facing, a significantly great number of mortalities and morbidities due to TB. Unfortunately, all previously reported treatments are not successful for the eradication of TB. Here in this study, we report an emerging treatment option for this disease. We have applied immunoinformatics to predict highly conserved B and T-cell epitopes from Mtb, showing significant binding affinities to the frequent HLA alleles in the Pakistani population. A total of ten highly referenced and experimentally validated epitopes were selected from the Immune Epitope Database (IEDB), followed by their conservancy analysis using weblogos. The consensus sequences and variants derived from these sequences were examined, for their binding affinities, with prevalent HLA alleles of Pakistan. Moreover, the antigenic and allergenic natures of these peptides were also evaluated via Vaxijen and AllerTOP, respectively. Consequently, all potentially allergenic and non-antigenic, peptide fragments, were excluded from the analysis. Among all putative epitopes, three CD8 + T-cell epitopes were selected, as ideal vaccine candidates and, population coverage analysis revealed that the combination of these three peptides was covering, 67.28% Pakistani Asian and 57.15% mixed Pakistani populations. Likewise, eleven linear and six conformational or discontinuous B-cell epitopes were also marked as potential vaccine candidates based on their prediction score, non-allergenic nature, and antigenic properties. These epitopes, however, need the final validation via wet-lab studies. After their approval, these epitopes would be effective candidates for the future designing of epitope-based vaccines against Mtb infections in Pakistan.Electronic supplementary materialThe online version of this article (10.1007/s10989-020-10111-w) contains supplementary material, which is available to authorized users.

Treg-inducing capacity of genomic DNA of Bifidobacterium longum subsp. infantis.

Background: Allergic and autoimmune diseases comprise a group of inflammatory disorders caused by aberrant immune responses in which CD25+ forkhead box P3-positive regulatory T cells (Treg) cells that normally suppress inflammatory events are often poorly functioning. This has stimulated an intensive investigative effort to find ways of increasing Tregs as a method of therapy for these conditions. Commensal microbiota known to have health benefits in humans include the lactic acid-producing, probiotic bacteria B. longum subsp. infantis and Lactobacillus rhamnosus. Mechanistically, several mechanisms have been proposed to explain how probiotics may favorably affect host immunity, including the induction of Tregs. Analysis of emerging data from several laboratories, including our own, suggest that DNA methylation may be an important determinant of immune reactivity responsible for Treg induction. Although methylated CpG moieties in normal mammalian DNA are both noninflammatory and lack immunogenicity, unmethylated CpGs, found largely in microbial DNA, are immunostimulatory and display proinflammatory properties. Objective: We hypothesize that microbiota with more DNA methylation may potentiate Treg induction to a greater degree than microbiota with a lower content of methylation. The purpose of the present study was to test this hypothesis by studying the methylation status of whole genomic DNA (gDNA) and the Treg-inducing capacity of purified gDNA in each of the probiotic bacteria B. longum subsp. infantis and L. rhamnosus, and a pathogenic Escherichia coli strain B. Results: We showed that gDNA from B. longum subsp. infantis is a potent Treg inducer that displays a dose-dependent response pattern at a dose threshold of 20 µg of gDNA. No similar Treg-inducing responses were observed with the gDNA from L. rhamnosus or E. coli. We identified a unique CpG methylated motif in the gDNA sequencing of B. longum subsp. infantis which was not found in L. rhamnosus or E. coli strain B. Conclusion: Although the literature indicates that both B. longum subsp. infantis and L. rhamnosus strains contribute to health, our data suggest that they do so by different mechanisms. Further, because of its small molecular size, low cost, ease of synthesis, and unique Treg-inducing feature, this methylated CpG oligodeoxynucleotide (ODN) from B. longum would offer many attractive features for an ideal novel therapeutic vaccine candidate for the treatment of immunologic diseases, such as the allergic and autoimmune disorders, in which Treg populations are diminished.